In order to further study relationship of structure and function of N- terminal human IFN-gamma, IFN-gamma peptide (-l to 18) was synthesized by the solid-phase technique of Merrifield. IFN-gamma peptide was digested wit SVs protease in buffer and resynthesized in organic solvent. We studied the effect of temperature, concentrations enzyme/peptide ratio and different organic solvents on reaction of digestion and resynthesis. We found digestion of IFN-gamma peptide in buffer was rapid. Greater than 90% of peptide was digested at 20 min RT using an enzyme/peptide ratio of 1/100 (w/w). The digestion products were analyzed by RP-HPLC. Five small peptides fragments were isolated and analyzed by RP-HPLC mini-gel system, amino acid sequence, CD spectra and bioassay. Enzymatic resynthesis proceeds with very high selectivity. Optimal condition for resynthesis was 80% 1-proponal enzyme/peptide ratio 1/600 (w/w) at RT. Resynthetic reaction attained an equilibrium approximately 16% in 24 hrs. Receptor binding assay of IFN-gamm peptide revealed the peptide had no receptor binding activity and antiviral activity. Studies are in progress to prepare antibodies to the peptide to assist in purifying the resynthesized IFN-gamma molecules.